Angel Falls, Venezuela

Angel Falls, Venezuela

The world's tallest waterfall was named one of 28 finalists in an international contest to decide the seven wonders of the natural world via popular vote. At 3,287 feet (1,002 meters) tall, Angel Falls is more than 19 times taller than North America's Niagara Falls.

The falls are also situated in a region full of tepuis—tabletop mountains unique to northern South America—which are "in danger from inappropriate or thoughtless resource development, like power lines cutting through scenic areas," National Geographic sustainable-tourism expert Jonathan Tourtellot said.

"Tepui country could do for more tourism as an economic counterforce for that kind of thoughtless development," added Tourtellot, who is also spearheading the second-annual Geotourism Challenge, where voters chose places "they consider most cutting edge in providing visitors with authentic travel experiences, whether in a big city or a remote spot."